Rotor cross-sectional structures

Consider the cross section of a rotor structure using a permanent magnet.
(1) is a cylindrical 2-pole SPM type. It is assumed that one ring-shaped magnet is used and that the lower part is magnetized to the N pole and the upper part to the S pole.
(2) is a structure using a segment type magnet.
(3) is a structure in which the cross section is circular, including the yoke. This type is rarely actually used. Removal of the magnet from this will result in
(4), which is a salient pole type and becomes the basic form of an SR motor. In other words, (3) is a combination of a permanent magnet and a reluctance motor.
(5) is a system that uses two permanent magnets of the same polarity, unlike (3), and it becomes a pseudo four pole. However, it is combined with a bipolar reluctance motor, so normal performance cannot be expected.
(6), instead, can incorporate a four-pole reluctance-motor structure by embedding a magnet. In other words, in this structure, the d axis and the q axis of 4 poles are formed and become the object model of vector control. On the other hand,
(7) is a four-pole SPM type. The photographs are examples of these two types, and they show contrasting characteristics.